A more recent development in semiconductor memory devices involves spin electronics, which combines semiconductor technology and magnetics. The spin of an electron, rather than the charge, is used to indicate the presence of a “1” or “0”. One such spin electronic device is a magnetic random access memory (MRAM) device 100, as shown in FIG. 1, which includes conductive lines (wordlines WL and bitlines BL) positioned in a different direction, e.g., perpendicular to one another in different metal layers, the conductive lines sandwiching a magnetic stack or magnetic tunnel junction (MTJ) 102, which functions as a magnetic memory cell. Shown in FIG. 2A, a current IWL flowing through one of the conductive lines WL generates a magnetic field around the conductive line WL and orients the magnetic polarity into a certain direction along the wire or conductive line. A current IBL flowing through the other conductive line BL induces the magnetic field and can partially turn the magnetic polarity, also. Digital information, represented as a “0” or “1”, is storable in the alignment of magnetic moments. The resistance of the magnetic memory cell 102 depends on the moment's alignment. The stored state is read from the magnetic memory cell 102 by detecting the component's resistive state.
An advantage of MRAM devices compared to traditional semiconductor memory devices such as dynamic random access memory (DRAM) devices is that MRAM devices are non-volatile. For example, a personal computer (PC) utilizing MRAM devices would not have a long “boot-up” time as with conventional PCs that utilize DRAM devices. Also, an MRAM device does not need to be powered up and has the capability of “remembering” the stored data. Therefore, MRAM devices are replacing flash memory, DRAM and static random access memory devices (SRAM) devices in electronic applications where a memory device is needed.
Because MRAM devices operate differently than traditional memory devices, they introduce design and manufacturing challenges. The speed of the write operation is a critical design feature of an MRAM device.